I upgraded to a i5-2500k and have questions

I've recently upgraded to a i5-2500k from an Athlon II X4 645. This is the first personal intel build I've done for myself. I have spent a huge amount of time with AMD and almost none with Intel, especially with overclocking.

Now I've got questions because some things are not consistent between the two companies.

First- Temps. My previous Athlon II x4 645 was cool. I slapped an Arctic Freezer 64 on it with Arctic Silver 5 and it idled at room temperature (16-17c) and never exceeded 35c on Prime95. All the cores stayed within one degree of each other and the heat was generally even.

I notice my shiny new i5-2500k is so much hotter despite lower power use and similar TDP. I put a CoolerMaster Hyper N520 on it (what I think is a better cooler), and it still idles in the 30c area and goes as high as 42c under Prime95 (all stock settings). That and my cores are all at different temps usually. Core #0 is the coolest, Core #1 is close to it, and Cores 2-3 run about 2-4c hotter than the others.

I've tried undervolting- It passed 29 hours of Prime95 at 1.01v, but the temps were only marginally better. Like 1-2c better.

Is uneven temps normal for Sandy Bridge Processors?

Is it normal for them to idle at higher temps and run hotter than AMD chips?

Can I not hit room temps at idle with air cooling? Are my temps to high for this cooler? (CoolerMaster Hyper N520)

What are safe temps for Intel chips? They similar to AMD's?

And for overclocking, I've gotten 4ghz at 1.1vcore and I'm now in the middle of running Prime95 for 24 hours on my 4.5ghz overclock at 1.25vcore (its been 8 hours and the hottest its gotten is 70c so far and that kinda scares me).

What are the usual voltages an i5-2500k needs to hit certain frequencies?

How much vcore do you think I need to pump into this to get 5ghz?

What are the 24/7 safe Vcore settings for Sandy Bridge?

What is considered a good overclocker when it comes to i5-2500k processors?

Oh, and one final thing: I've never seen my processor at 3.3ghz at stock settings. It stays at 3.4ghz almost 100% of the time it is not in idle, even in Prime95 for 29 hours. If not that, then higher. That's good, but is that normal for everyone?

Ok, rather than write a tech version of War and Peace, I'd point you towards a couple of good-ish OC guides for 2500K/2600K.

A couple of points I would add. The Rosewill chassis is ok -not great. I think the fans are ~35cfm are they not (similar to Silverstone?).
The CM cooler is also in the same category. 2500K/2600K run pretty cool and at stock, but once you start pushing up Vcore the heat production does ramp accordingly. The N520 isn't a bad performer but it could be hampered by limited chassis cooling.

Bear in mind that most reviews would test overclock with resultant temps using a high-end air cooler or water, either in a full-size tower or open bench stand. Both the choice of cooler and chassis have a marked effect on temps....I'd be more than a little surprised if your Athlon II got anywhere close to the clock/temp ratio using the same basic setup.

Having said that, not all 2500K/2600K are created equal. D1 revision typically requires more voltage (and hence more heat dissipation) than D2 revision...and both D1 and D2 clock easier than D0 (Engineering samples). In addition some FPO batches also have better VID and OC characteristics. There is quite a market for certain FPO's and numerous threads devoted to the subject. As such -and as with most CPU's- buying a single off-the-shelf CPU is basically luck of the draw.
And in answer to your question- Yes, different core temps are pretty much standard for any quad-core- although they usually aren't too disparate if you are running a stress test (all cores at 100%)
Also:
1.25v is not bad for 4.5G. Seen better, seen a few worse.
- Is 1.25v set in the UEFI, or is it what's reported in CPU-Z (or similar monitoring software) i.e. voltage after Vdroop